Aristotle placed much more value on knowledge gained from the senses and would correspondingly be better classed among modern empiricists (see materialism and empiricism). He also achieved a "grounding" of dialectic in the Topics by allowing interlocutors to begin from commonly held beliefs (Endoxa); his goal being non-contradiction rather than Truth. He set the stage for what would eventually develop into the empiricist version of scientific method centuries later. Although he wrote dialogues early in his career, no more than fragments of these have survived. The works of Aristotle that still exist today are in treatise form and were, for the most part, unpublished texts. These were probably lecture notes or texts used by his students, and were almost certainly revised repeatedly over the course of years. As a result, these works tend to be eclectic, dense and difficult to read. Among the most important ones are Physics, Metaphysics, Nicomachean Ethics, Politics, De Anima (On the Soul) and Poetics.
These works, although connected in many fundamental ways, are very different in both style and substance.

Contents

A bust of Aristotle is a nearly ubiquitous ornament in places of high culture in the West.

Aristotle was born at Stageira, a colony of Andros on the Macedonian peninsula of Chalcidice in 384 BC. His father, Nicomachus, was court physician to King Amyntas III of Macedon. It is believed that Aristotle's ancestors held this position under various kings of the Macedons. As such, Aristotle's early education would probably have consisted of instruction in medicine and biology from his father. About his mother, Phaestis, little is known. It is known that she died early in Aristotle's life. When Nicomachus also died, in Aristotle's tenth year, he was left an orphan and placed under the guardianship of his uncle, Proxenus of Atarneus. He taught Aristotle Greek, rhetoric, and poetry (O'Connor et al., 2004). Aristotle was probably influenced by his father's medical knowledge; when he went to Athens at the age of 18, he was likely already trained in the investigation of natural phenomena.

From the age of 18 to 37 Aristotle remained in Athens as a pupil of Plato and distinguished himself at the Academy. The relations between Plato and Aristotle have formed the subject of various legends, many of which depict Aristotle unfavourably. No doubt there were divergences of opinion between Plato, who took his stand on sublime, idealistic principles, and Aristotle, who even at that time showed a preference for the investigation of the facts and laws of the physical world. It is also probable that Plato suggested that Aristotle needed restraining rather than encouragement, but not that there was an open breach of friendship. In fact, Aristotle's conduct after the death of Plato, his continued association with Xenocrates and other Platonists, and his allusions in his writings to Plato's doctrines prove that while there were conflicts of opinion between Plato and Aristotle, there was no lack of cordial appreciation or mutual forbearance. Besides this, the legends that reflect Aristotle unfavourably are traceable to the Epicureans, who were known as slanderers. If such legends were circulated widely by patristic writers such as Justin Martyr and Gregory Nazianzen, the reason lies in the exaggerated esteem Aristotle was held in by the early Christianheretics, not in any well-grounded historical tradition.

After the death of Plato (347 BC), Aristotle was considered as the next head of the Academy, a post that was eventually awarded to Plato's nephew. Aristotle then went with Xenocrates to the court of Hermias, ruler of Atarneus in Asia Minor, and married his niece and adopted daughter, Pythia. In 344 BC, Hermias was murdered in a rebellion, and Aristotle went with his family to Mytilene. It is also reported that he stopped on Lesbos and briefly conducted biological research. Then, one or two years later, he was summoned to Pella, the Macedonian capital, by King Philip II of Macedon to become the tutor of Alexander the Great, who was then 13.

Plutarch wrote that Aristotle not only imparted to Alexander a knowledge of ethics and politics, but also of the most profound secrets of philosophy. We have much proof that Alexander profited by contact with the philosopher, and that Aristotle made prudent and beneficial use of his influence over the young prince (although Bertrand Russell disputes this). Due to this influence, Alexander provided Aristotle with ample means for the acquisition of books and the pursuit of his scientific investigation.

It is possible that Aristotle also participated in the education of Alexander's boyhood friends, which may have included for example Hephaestion and Harpalus. Aristotle maintained a long correspondence with Hephaestion, eventually collected into a book, unfortunately now lost.

According to sources such as Plutarch and Diogenes, Philip had Aristotle's hometown of Stageira burned during the 340s BC, and Aristotle successfully requested that Alexander rebuild it. During his tutorship of Alexander, Aristotle was reportedly considered a second time for leadership of the Academy; his companion Xenocrates was selected instead.

In about 335 BC, Alexander departed for his Asiatic campaign, and Aristotle, who had served as an informal adviser (more or less) since Alexander ascended the Macedonian throne, returned to Athens and opened his own school of philosophy. He may, as Aulus Gellius says, have conducted a school of rhetoric during his former residence in Athens; but now, following Plato's example, he gave regular instruction in philosophy in a gymnasium dedicated to Apollo Lyceios, from which his school has come to be known as the Lyceum. (It was also called the Peripatetic School because Aristotle preferred to discuss problems of philosophy with his pupils while walking up and down -- peripateo -- the shaded walks -- peripatoi -- around the gymnasium).

During the thirteen years (335 BC–322 BC) which he spent as teacher of the Lyceum, Aristotle composed most of his writings. Imitating Plato, he wrote Dialogues in which his doctrines were expounded in somewhat popular language. He also composed the several treatises (which will be mentioned below) on physics, metaphysics, and so forth, in which the exposition is more didactic and the language more technical than in the Dialogues. These writings show to what good use he put the resources Alexander had provided for him. They show particularly how he succeeded in bringing together the works of his predecessors in Greek philosophy, and how he pursued, either personally or through others, his investigations in the realm of natural phenomena. Pliny claimed that Alexander placed under Aristotle's orders all the hunters, fishermen, and fowlers of the royal kingdom and all the overseers of the royal forests, lakes, ponds and cattle-ranges, and Aristotle's works on zoology make this statement more believable. Aristotle was fully informed about the doctrines of his predecessors, and Strabo asserted that he was the first to accumulate a great library.

During the last years of Aristotle's life the relations between him and Alexander became very strained, owing to the disgrace and punishment of Callisthenes, whom Aristotle had recommended to Alexander. Nevertheless, Aristotle continued to be regarded at Athens as a friend of Alexander and a representative of Macedonia. Consequently, when Alexander's death became known in Athens, and the outbreak occurred which led to the Lamian war, Aristotle shared in the general unpopularity of the Macedonians. The charge of impiety, which had been brought against Anaxagoras and Socrates, was now, with even less reason, brought against Aristotle. He left the city, saying (according to many ancient authorities) that he would not give the Athenians a chance to sin a third time against philosophy. He took up residence at his country house at Chalcis, in Euboea, and there he died the following year, 322 BC. His death was due to a disease, reportedly 'of the stomach', from which he had long suffered. The story that his death was due to hemlock poisoning, as well as the legend that he threw himself into the sea "because he could not explain the tides," is without historical foundation.

Very little is known about Aristotle's personal appearance except from hostile sources. The statues and busts of Aristotle, possibly from the first years of the Peripatetic School, represent him as sharp and keen of countenance, and somewhat below the average height. His character—as revealed by his writings, his will (which is undoubtedly genuine), fragments of his letters and the allusions of his unprejudiced contemporaries—was that of a high-minded, kind-hearted man, devoted to his family and his friends, kind to his slaves, fair to his enemies and rivals, grateful towards his benefactors. When Platonism ceased to dominate the world of Christian speculation, and the works of Aristotle began to be studied without fear and prejudice, the personality of Aristotle appeared to the Christian writers of the 13th century, as it had to the unprejudiced pagan writers of his own day, as calm, majestic, untroubled by passion, and undimmed by any great moral defects, "the master of those who know".

Aristotle's legacy also had a profound influence on Islamic thought and philosophy during the middle ages. The likes of Avicenna, Farabi, and Yaqub ibn Ishaq al-Kindi1 were a few of the major proponents of the Aristotelian school of thought during the Golden Age of Islam.

Aristotle defines philosophy in terms of essence, saying that philosophy is "the science of the universal essence of that which is actual". Plato had defined it as the "science of the idea", meaning by idea what we should call the unconditional basis of phenomena. Both pupil and master regard philosophy as concerned with the universal; Aristotle, however, finds the universal in particular things, and called it the essence of things, while Plato finds that the universal exists apart from particular things, and is related to them as their prototype or exemplar. For Aristotle, therefore, philosophic method implies the ascent from the study of particular phenomena to the knowledge of essences, while for Plato philosophic method means the descent from a knowledge of universal ideas to a contemplation of particular imitations of those ideas. In a certain sense, Aristotle's method is both inductive and deductive, while Plato's is essentially deductive.

In Aristotle's terminology, the term natural philosophy corresponds to the phenomena of the natural world, which include: motion, light, and the laws of physics. Many centuries later these subjects would become the basis of modern science, as studied through the scientific method. In modern times the term philosophy has come to be more narrowly understood as metaphysics, distinct from empirical study of the natural world via the physical sciences. In constrast, in Aristotle's time and use philosophy was taken to encompass all facets of intellectual inquiry.

In the larger sense of the word, he makes philosophy coextensive with reasoning, which he also called "science". Note, however, that his use of the term science carries a different meaning than that which is covered by the scientific method. "All science (dianoia) is either practical, poetical or theoretical." By practical science he understands ethics and politics; by poetical, he means the study of poetry and the other fine arts; while by theoretical philosophy he means physics, mathematics, and metaphysics.

The last, philosophy in the stricter sense, he defines as "the knowledge of immaterial being," and calls it "first philosophy", "the theologic science" or of "being in the highest degree of abstraction." If logic, or, as Aristotle calls it, Analytic, be regarded as a study preliminary to philosophy, we have as divisions of Aristotelian philosophy (1) Logic; (2) Theoretical Philosophy, including Metaphysics, Physics, Mathematics, (3) Practical Philosophy; and (4) Poetical Philosophy.

Aristotle "says that 'on the subject of reasoning' he 'had nothing else on an earlier date to speak about'" (Bocheński, 1951). However, Plato reports that syntax was thought of before him, by Prodikos of Keos, who was concerned by the right use of words. Logic seems to have emerged from dialectics; the earlier philosophers used concepts like reductio ad absurdum as a rule when discussing, but never understood its logical implications. Even Plato had difficulties with logic. Although he had the idea of constructing a system for deduction, he was never able to construct one. Instead, he relied on his dialectic, which was a confusion between different sciences and methods (Bocheński, 1951). Plato thought that deduction would simply follow from premises, so he focused on having good premises so that the conclusion would follow. Later on, Plato realised that a method for obtaining the conclusion would be beneficial. Plato never obtained such a method, but his best attempt was published in his book Sophist, where he introduced his division method (Rose, 1968).

What we call today Aristotelian logic, Aristotle himself would have labelled analytics. The term logic he reserved to mean dialectics. Most of Aristotle's work is probably not authentic, since it was most likely edited by students and later lecturers. The logical works of Aristotle were compiled into six books at about the time of Christ:

Categories

On Interpretation

Prior Analytics

Posterior Analytics

Topics

On Sophistical Refutations

The order of the books (or the teachings from which they are composed) is not certain, but this list was derived from analysis of Aristotle's writings. There is one volume of Aristotle's concerning logic not found in the Organon, namely the fourth book of Metaphysics. (Bocheński, 1951).

Aristotle is also the creator of syllogisms with modalities (modal logic). The word modal refers to the word 'modes', explaining the fact that modal logic deals with the modes of truth. Aristotle introduced the qualification of 'necessary' and 'possible' premises. He constructed a logic which helped in the evaluation of truth but which was very difficult to interpret. (Rose, 1968).

Aristotelian discussions about science had only been qualitative, not quantitative. By the modern definition of the term, Aristotelian philosophy was not science, as this worldview did not attempt to probe how the world actually worked through experiment. For example, in his book The history of animals he claimed that human males have more teeth than females. Had he only made some observations, he would have discovered that this claim is false.

Rather, based on what one's senses told one, Aristotelian philosophy then depended upon the assumption that man's mind could elucidate all the laws of the universe, based on simple observation (without experimentation) through reason alone.

One of the reasons for this was that Aristotle held that physics was about changing objects with a reality of their own, whereas mathematics was about unchanging objects without a reality of their own. In this philosophy, he could not imagine that there was a relationship between them.

In contrast, today's "science" assumes that thinking alone often leads people astray, and therefore one must compare one's ideas to the actual world through experimentation; only then can one see if one's ideas are based in reality. This position is known as empiricism or the scientific method.

Aristotle names four "causes" of things, but the word cause (Greek: αἰτἱα, aitia) is not used in the modern sense of "cause and effect", under which causes are events or states of affairs. Rather, the four causes are like different ways of explaining something:

This is the blueprint or the idea commonly held of what an object should be. Aristotle says, "The form is the account (and the genera of the account) of the essence (for instance, the cause of an octave is the ratio two to one, and in general number), and the parts that are in the account."

This is the person who makes an object, or "unmoved movers" (gods) who move nature. For example, "a father is a cause of his child; and in general the producer is a cause of the product and the initiator of the change is a cause." This is closest to the modern definition of "cause".

The final cause or telos is the purpose or end that something is supposed to serve. This includes "all the intermediate steps that are for the end ... for example, slimming, purging, drugs, or instruments are for health; all of these are for the end, though they differ in that some are activities while others are instruments."

An example of an artifact that has all four causes would be a table, which has material causes (wood and nails), a formal cause (the blueprint, or a generally agreed idea of what tables are), an efficient cause (the carpenter), and a final cause (using it to dine on).

Aristotle argues that natural objects such as an "individual man" have all four causes. The material cause of an individual man would be the flesh and bone that make up an individual man. The formal cause would be the blueprint of man, that which is used as a guide to create an individual man and to keep him in a certain state called man. The efficient cause of an individual man would be the father of that man, or in the case of all men an "unmoved mover" who breathed (anima: breath) into the soul (anima: soul) of man. The final cause of man would be as Aristotle stated, "Now we take the human's function to be a certain kind of life, and take this life to be the soul's activity and actions that express reason. Hence the excellent man's function is to do this finely and well. Each function is completed well when its completion expresses the proper virtue. Therefore the human good turns out to be the souls' activity that expresses virtue."

The difference between natural objects and an artifact is that natural objects have self movement. Aristotle defined the difference between a natural object and an artifact when he stated, "In contrast to these, a bed, a cloak, or any other artifact-insofar as it is described as such i.e., as a bed, a cloak, or whatever, and to the extent that it is a product of a craft-has no innateimpulse to change; but insofar as it is coincidentally made of stone or earth or a mixture of these, it has an innate impulse to change and just to that extent. This is because a nature is a type of principle and cause of motion and stability within those things to which it primarily belongs in their own right and not coincidentally." The natural objects are changed to artifacts through crafts but they have an innate impulse of self movement to convert through time to their natural state, and they will all turn into that state when all animals with reason are extinct from the earth.

Chance lies in the realm of accidental causes. It is "from what is spontaneous" (but note that what is spontaneous does not come from chance). For a better understanding of Aristotle's conception of "chance" it might be better to think of "coincidence": Something takes place by chance if a person sets out with the intent of having one thing take place, but with the result of another thing (not intended) taking place. For example: A person seeks donations. That person may find another person willing to donate a substantial sum. However, if the person seeking the donations met the person donating, not for the purpose of collecting donations, but for some other purpose, Aristotle would call the collecting of the donation by that particular donator a result of chance. It must be unusual that something happens by chance. In other words, if something happens all or most of the time, we cannot say that it is by chance.

However, chance can only apply to human beings. According to Aristotle, chance must involve choice (and thus deliberation), and only humans are capable of deliberation and choice. "What is not capable of action cannot do anything by chance" (Physics, 2.6).

Although Aristotle wrote several works on ethics, the major one was the Nicomachean Ethics, which is considered one of Aristotle's greatest works; it discusses virtues. The ten books which comprise it are based on notes from his lectures at the Lyceum and were either edited by or dedicated to Aristotle's son, Nicomachus.

Aristotle believed that ethical knowledge is not certain knowledge (like metaphysics and epistemology) but is general knowledge. Also, as it is not a theoretical discipline, he thought a person had to study in order to become "good." Thus, if a person was to become virtuous, they could not simply study what virtue is, they had to actually do virtuous activity.
In order to do this, Aristotle had to first establish what was virtuous. He began by determining that everything was done with some goal in mind and that goal is 'good.' The ultimate goal he called the Highest Good.

Aristotle contested that happiness could not be found only in pleasure or only in fame and honor. He finally finds happiness "by ascertaining the specific function of man. But what is this function that will bring happiness? To determine this, Aristotle analyzed the soul and found it to have three parts: the Nutritive Soul (plants, animals and humans), the Perceptive Soul (animals and humans) and the Rational Soul (humans only). Thus, a human's function is to do what makes it human, to be good at what sets it apart from everything else: the ability to reason or Nous. A person that does this is the happiest because they are fulfilling their purpose or nature as found in the rational soul. Depending on how well they did this, Aristotle said people belonged to one of four categories: the Virtuous, the Continent, the Incontinent and the Vicious.

Aristotle believes that every ethical virtue is an intermediate condition between excess and deficiency. This does not mean Aristotle believed in moral relativism, however. He set certain emotions (e.g., hate, envy, jealousy, spite, etc.) and certain actions (e.g., adultery, theft, murder, etc.) as being always wrong, regardless of the situation or the circumstances.

In Nicomachean Ethics, Aristotle focuses on the importance of continually behaving virtuously and developing virtue rather than committing specific good actions. This can be contrasted with Kantian ethics, in which the primary focus is on individual action. Nicomachean Ethics emphasizes the importance of context to ethical behaviour — what might be right in one situation might be wrong in another. Aristotle believed that happiness is the end of life and that as long as a person is striving for goodness, good deeds will result from that struggle, making the person virtuous and therefore happy.

Plato (left) and Aristotle (right), a detail of The School of Athens, a fresco by Raphael. Aristotle gestures to the earth, representing his belief in knowledge through empirical observation and experience.

Aristotle has been criticised on several grounds.

His analysis of procreation is frequently criticised on the grounds that it presupposes an active, ensouling masculine element bringing life to an inert, passive, lumpen female element; it is on these grounds that some feminist critics refer to Aristotle as a misogynist.

At times, the objections that Aristotle raises against the arguments of his own teacher, Plato, appear to rely on faulty interpretations of those arguments.

Although Aristotle advised, against Plato, that knowledge of the world could only be obtained through experience, he frequently failed to take his own advice. Aristotle conducted projects of careful empirical investigation, but often drifted into abstract logical reasoning, with the result that his work was littered with conclusions that were not supported by empirical evidence: for example, his assertion that objects of different mass fall at different speeds under gravity, which was later refuted by John Philoponus (credit is often given to Galileo, even though Philopinus lived centuries earlier).

In the Middle Ages, roughly from the 12th century to the 15th century, the philosophy of Aristotle became firmly established dogma. Although Aristotle himself was far from dogmatic in his approach to philosophical inquiry, two aspects of his philosophy might have assisted its transformation into dogma. His works were wide-ranging and systematic so that they could give the impression that no significant matter had been left unsettled. He was also much less inclined to employ the skeptical methods of his predecessors, Socrates and Plato.

Some academics have suggested that Aristotle was unaware of much of the current science of his own time.

Aristotle was called not a great philosopher, but "The Philosopher" by Scholastic thinkers. These thinkers blended Aristotelian philosophy with Christianity, bringing the thought of Ancient Greece into the Middle Ages. It required a repudiation of some Aristotelian principles for the sciences and the arts to free themselves for the discovery of modern scientific laws and empirical methods.

Though we know that Aristotle wrote many elegant treatises (Cicero described his literary style as "a river of gold"), the originals have been lost in time. All that we have now are the literary notes for his pupils, which are often difficult to read (the Nicomachean Ethics is a good example). It is now believed that we have about one fifth of his original works.

Aristotle underestimated the importance of his written work for humanity. He thus never published his books, except from his dialogues. The story of the original manuscripts of his treatises is described by Strabo in his Geography and Plutarch in his "Parallel Lives, Sulla": The manuscripts were left from Aristotle to Theophrastus, from Theophrastus to Neleus of Scepsis, from Neleus to his heirs. Their descendants sold them to Apellicon of Teos. When Sulla occupied Athens in 86 BC, he carried off the library of Appellicon to Rome, where they were first published in 60 BC from the grammarian Tyrranion of Amisus and then by philosopher Andronicus of Rhodes.

The extant works of Aristotle are broken down according to the five categories in the Corpus Aristotelicum. Not all of these works are considered genuine, but differ with respect to their connection to Aristotle, his associates and his views. Some, such as the Athenaion Politeia or the fragments of other politeia are regarded by most scholars as products of Aristotle's "school" and compiled under his direction or supervision. Other works, such On Colours may have been products of Aristotle's successors at the Lyceum, e.g., Theophrastus and Straton. Still others acquired Aristotle's name through similarities in doctrine or content, such as the De Plantis, possibly by Nicolaus of Damascus. A final category, omitted here, includes medieval palmistries, astrological and magical texts whose connection to Aristotle is purely fanciful and self-promotional. Those that are seriously disputed are marked with an asterisk.

On Melissus, On Xenophanes, and On Gorgias. These are sometimes grouped together and called the "MXG" writings. They clearly are not written by Aristotle, and are believed to date from the fifth century AD. However, because they have frequently been attributed to him in the past, they are often included in compilations of his writings (for example, in the Loeb Classical Library).